Vapor phase extraction



Feb. 24, 1948.

w. B. FRANKLIN 2,436,473

VAPOR PHASE EXTRACTION.

Filed May 15, 194% Buiylenes Nuphi'hu Butylenes Burodiene Butylanes g4 Hydrocarbons to 'n afiiudiiw J ATTORNEY- iatented Feb. 24, 1 948 merit Company, Eliz ofiDelaware 1 .42. .411 *yAPoaP-H-Asr: EXTRACTION swilliam; B.-.Franklin, Baytown, \Tex .assig lqplliy :mesneassignments, to StaridarfdiOiLDevelopabethJN. 11,, j a. corporation tApplicationeMayz l g, 1946, Serial No. 669,273

The present application r-is {a continua-tionv'inpart of my copending application .Serial -No.

547,595; filed :August :1, 11944, which has become abandoned.

The present invention is directeditoeamrocess in -whichra-nmixture. of gaseousor vaporous con- 'stituents -.is s'scrubbed :with a liguid r capable :of taking up one-ortmoresofrsaid constituents. A

- particular process of thistgeneral type to-which the present invention is: especially applicable is the recovery of butadieneirom a mixture. of G4 hydrocarbons containing itby-scnubbing them-ixturewith an .ammoniacalzsolution .of- .cuproussacetate.

It has been found: that theefliciency. of-a scrubbing operation of the aforesaid type is greatlyincreased byaadding tothascrubbing liquid another liquid chemically inert to the scrubbing liquid and to the gaseousconstit'ue'ntsbeing treated but having high solvent, powenfor such constituents. -In the ordinary case, this second-liquid will also be immiscible With the scrubbing liquid. The second liquid apparently serves as aparrierfor bringing the gaseous substances into intimate contact-with the scrubbing liquid. Flor;;purposes of discussion, this second -liquid will be hereafter referred: to. as a carrier liquid.

In the particular operation heretofore mentioned, in which C4 hydrocarbons are scrubbed with an ammoniacal solution of cuprous acetate, an excellent carrier liquid is naphtha of a boiling range as low as possible considering that it must remain in the liquid phase at the temperature at which the scrubbing operation is performed. N aphtha has substantially no selectivity for butadiene. Therefore-it absorbs all of the C4 hydrocarbons. Consequently, it is not advantageous to use a large quantity of naphtha because if this were subjected to desorption with ammoniacal cuprous acetate solution, it would be impossible to obtain pure butadiene, The amount of naphtha, therefore, is held at a minimum. It has been found that in this particular operation an amount of naphtha not in excess of 0.1% by volume of the copper salt solution eifectively functions to increase the scrubbing efliciency of the latter.

The nature of the present invention may be better understood from the following detailed description of the accompanying drawing in which the single figure is a front elevation in diagrammatic form of a plant embodying said invention.

Referring to the drawing in detail, numeral I designates a scrubbing tower. The gases to be scrubbed are introduced into an intermediate point of said tower by line 2. A scrubbing medium is introduced into the upper part of said tower by line 3. Unabsorbed gases leave the top of the tower through line 4. The scrubbing liquid, with its absorbed constituents, leaves the bottom of :6 Claims. (CL 260- 6815) 4 thetowerthrough,linell'aby whiciritis conducted to a desorptiontewerii.

:Entering the-top .or .tower .6 .the .fa-t scrubbing liquid descendsgthroughthedesorber. eithercounte rcurrent to. azsuitablestri-pping medium. or with agradually increasing temperature .which .serves to .liberate the absorbed gaseous constituents. The lean. scrubbing-medium.leavesthe :bottom of desorber -6 through line T1 .whichicarries vit back to --line 3. Suitabla'heat exchangersv are arranged in: lines..2 5 and "l fonefiicient-utilization otheat.

The liberatedgaseoius constituent leaves-the top of. the .desorber'ithrough lineiB. 'Incertain cases it maybe desirable toitakeofi..the,.purified.=.gaseous constitue'ntas aside streammhroughlineiil. Line 8 connects-both --with' line-'. 9.-and withnthe bottom of tower 'l.

.Intthe :particulanonerationealready referred. to,

thefeed .tol thescrubbingttowerl his a mixture .of

C4 hydrocarbons containing .butadiene. "I'he scrubbing medium is an ammoniacal-rsolution of .cuprous acetate. .The scrubbingtower.iscperated at. a. pressure .ranging from atmospheric .to. .about 8 pounds-per squaredncmgauge. :A-temperature of about-25 Fa is,maintained,in thesuppenpartof the tower andta -temperature:-ibetween about .50" and" 55 F. is maintained in the lower part of the tower. In the desorber, heaters are provided which maintain a temperature graduating from about F. at the top of the tower to about 165 F. at the bottom. Naphtha is introduced into line 3 through line 10.

In this operation it is customary to by-pass the recycled copper salt solution from line I to an incorporator I l ahead of which is arranged a feed line 12 for liquid butylenes. The mixture leaving the incorporator is passed to a settler l3 from the bottom of which the copper salt solution is returned to line 1. The purpose of this washing step is to remove from the copper salt solution Per cent Butadiene 25 Isobutylene 30 N-butylene 42 Butanes 3 Total This mixture is fed to the tower at a rate of 10,000

. pounds per hour. The copper salt solution is fed is connected to the desorber at a point below the point of introduction of the fat scrubbing me dium. Line 8, being connected above'the latter point, carries ofi gaseous constituents which are first flashed off from the iatscrubbing medium and, therefore, it carries less. pure butadiene. Part of the butadiene in line 8 is injected to the bottom of scrubbing tower l for further purification.

blng liquid an, amountof a hydrocarbon carrier liquid not substantially in excess of 0.1% by volume of the scrubbing liquid which is immiscible therewith and chemically inert to the scrubbing liquid and to the gaseous constituents undergoing "treatment and having strong solvent power for u said gaseous constituents.

It will be understood that the foregoing specific illustration of the process of the present invention is not intended to delineate the scope of the present invention. The use of a carrier liquid in the manner described finds application in other processes of this type. It is to be noted that while naphtha has been designated as thecarrierliquids in the particular operation described, other liq uids, such as kerosene and light gas oil, having suitable boiling point and chemical inertness to the gaseous constituents being treated-and sufli cient solvent power for said gaseous constituents may be employed. Similarly, while an ammoniacal solution of cuprou acetate has been designated as, the preferred scrubbing liquid, other liquids which will absorb by chemical action and desorb by the application of heat, as for example water, ammoniacal water, and aqueous solutions of silver nitrate, mercuric cyanide, and cuprous chloride, may also be used.

The nature and objects of the present invention having been fully described and illustrated, what .I desire to claim as new and useful and to secure ,by Letters Patent is: g

1. In a process in which a mixture of gaseous 2. In a process in which a mixture of gaseous hydrocarbons containing butadiene is scrubbed with an aqueous metallic salt solution which is liquid and capable of selectively taking up said butadiene, the step of adding to the scrubbing liquid an amount of a hydrocarbon carrier liquid not substantially in excess of 0.1% by volume of said scrubbing liquid.

3. A method according to claim 2 in which the carrier liquid is a naphtha.

4. A process according to claim 2 in which the scrubbing liquid is an ammoniacal solution of cu'prous acetate.

"5. A method according to claim 2 in which the scrubbing liquid is an ammoniacal solution of cuprous acetate and the carrier liquid is naphtha.

6. In a process in which a mixture of gaseous constituents containing butadiene is scrubbed with an ammoniacal solution of cuprous acetate for the selective removal of butadiene therefrom, the step of adding to the cuprous acetate solution an amount of naphtha not substantially in excess of .1% by volume of said solution.

WILLIAM B. FRANKLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,365,898 Morris et al Dec. 26, 1944 2,384,378 Hooker et a1 Sept. 4, 1945 

